Very much a northern species, the Bottlebrush Hydroid, Thuiaria thuja, is very distinctive and unlikely to be confused with any other hydroid. Growing to a maximum of 25cms, it occurs as far down as Northumberland on the east and the northern end of the Outer Hebrides on the west. It appears to prefer areas of strong tidal movement where its polyps trap plankton.
St. Abbs Marine Reserve, Berwickshire. Scotland